This invention relates to a mass spectrometer, in particular to a mass spectrometer, in which the central orbit of ions can be easily adjusted so that ions to be measured having a predetermined mass number pass through the center of the exit of the device.
Heretofore, for a quadrupole lens in this sort of device, a method is employed by which only DC voltages are applied to each of the pairs of opposing electrodes. This method is very useful for transmitting ions with a high efficiency. Although it is desirable that ions to be measured having a predetermined mass number pass through the center of the exit of the device, in this sort of device it was impossible to judge whether the central orbit of ions pass through the center of the quadrupole lens. This sort of device is described e.g. in the article entitled "High-resolution High-sensitivity Mass Spectrometers" by H. Matsuda in Mass Spectrometry Reviews, Volume 2, No. 2, 1983.